1. Field of the Invention
The present invention relates to a sheet conveyance apparatus and an image forming apparatus.
2. Description of the Related Art
Heretofore, there has been known a feeding option which can be attached to an image forming apparatus main body in Japanese Patent Application Laid-Open No. 2007-261705. Unlike anything that is originally mounted on an image forming apparatus when the apparatus is manufactured, the feeding option is the one that a user optionally adds to an image forming apparatus being a finished product to add functions and enhance performances thereof. The feeding option is sold separately from the image forming apparatus being the finished product, and used after a purchaser combining the feeding option with the image forming apparatus being the finished product. Some of the feeding options can store a large amount of sheets and sheets different in sizes.
The image forming apparatus on which the feeding option is mounted can form an image not only on a sheet fed from a sheet feeding unit of the image forming apparatus main body but also on a sheet fed from the feeding option to the image forming apparatus main body.
When the feeding option feeds a sheet to the image forming apparatus main body, dispersion sometimes occurs among timings of when a sheet conveyed from the feeding option reaches the image forming apparatus main body. A reason the dispersion occurs seems to be due to a state where the sheets are set on the feeding option, the friction resistance between the sheets, slippage between a roller and the sheet, and the dispersion of start of drive operation.
If a sheet conveyed from the feeding option reaches the image forming apparatus main body earlier than a predetermined timing, the image forming apparatus main body decreases the sheet conveyance speed to cause the timing of the sheet to agree with a timing of a transfer unit. Then, the sheet conveyance speed in the image forming apparatus main body becomes lower than that in the feeding option to deform the sheet conveyed between the image forming apparatus main body and the feeding option in the direction in which the sheet is bent.
When the sheet is deformed in the direction in which the sheet is bent, the sheet applies a pushing force against a conveyance roller in the feeding option in the direction opposite to the conveyance direction to increase a load applied to a drive unit for driving the conveyance roller. This increases a torque required for the drive unit for driving the conveyance roller in the feeding option, which may increase the size and cost of the apparatus.